Corals reefs are dying at an unprecedented rate, due in large part to a brightly colored predatory invader.
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| Weakened reefs provide a banquet for the crown of thorns starfish. |
| © MIT |
New studies by researchers at the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University found that coral mortality is accelerating faster than at any point during the last 11,000 years. Reefs across the Indo-Pacific region are especially at risk. Along with bleaching and disease, the alien species known as the crown of thorns starfish is having a devastating impact on the Great Barrier Reef and other important coral formations.
The starfish feeds off reefs by eating coral polyps and can wreak havoc on ecosystems. Just one specimen can consume 64 square feet of reef each year. Charles Birkeland, one of the world’s foremost experts on the crown of thorns, has written that the animal “has been of greater concern for [reef] management...than any other species of marine organism.” Both Australia and Okinawa, Japan, which house some of the richest marine ecosystems on Earth, have been beset by crown of thorn infestations.
Ecologists have rallied around removal efforts. But getting the predators out of the ocean is far from the main issue for reefs, says Robert Bolland, a marine biologist working at the University of Maryland’s Okinawa campus. The outbreaks are “primarily a function of man’s activity on land,” he says, and to really assess the problem requires a broader perspective.
Erosion and sediment runoff from agriculture chokes reefs. The crown of thorns has difficulty latching onto healthy reefs because active coral polyps are able to eat the starfish while they are still in larval form. Recent damage to reefs in the region has undermined reef health and resistance to infestation. Bolland contends that simply concentrating on plucking the crown of thorns out of the water shifts the focus away from development’s substantial role in the problem.
Rates of recovery differ. After a major starfish outbreak in the 1970s, the Great Barrier Reef was able to bounce back well over the course of a few decades due to comprehensive management efforts. Other reefs still suffer, though, and Bolland is skeptical that Okinawa’s weakened coral stands will rejuvenate any time soon. “In my lifetime, I’ll never see live corals out here like I did 15 years ago,” he says.
—Jeff Shaw
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